Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-07-08
2001-05-15
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S208100, C362S297000, C358S475000
Reexamination Certificate
active
06232592
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light guide member, an illumination device, and an image reading apparatus using them and, more particularly, to an apparatus for illuminating an original with a linear light beam while optically illuminating, guiding the light beam from the original onto a light-receiving surface to form an original image, and reading the original image.
2. Related Background Art
FIG. 1
is a view for explaining a prior art (Japanese Patent Application Laid-Open No. 9-61633). A light beam from a light-emitting member
41
is incident on a columnar light guide member
45
from its end portion and propagates in the columnar light guide member
45
. The light beam illuminating a light-diffusing portion
43
is diffused, and part of the diffused light beam emerges downward from a light emergent portion
44
in FIG.
1
.
FIG. 2
is a view for explaining an optical path when the prior art in
FIG. 1
is applied to an image reading apparatus. Reference numeral
46
in
FIG. 1
denotes an imaging lens of an image reading system; and
47
, a transmission original.
In this apparatus, light beam from the light-emitting member
41
enters into the columnar light guide member
45
from a light incident surface
42
at the end portion of the light guide member
45
and propagates through the light guide member
45
. The light beam then emerges outside the light guide member
45
from the light emergent portion
44
formed on the outer surface along the longitudinal direction. The exit light beam illuminates the transmission original
47
. An image of the transmission original
47
illuminated with the light beam is formed on the surface of a light-receiving element (not shown) by the imaging lens
46
, thereby reading the image.
Generally, in an illumination device using a light guide member, of all the light beams repeating total reflection in the light guide member, light beam that does not satisfy the total reflection condition on the inner wall of the light guide member and emerges outside the light guide member is used to illuminate the original. When a reflection/diffusion surface is formed on the surface opposing the light emergent surface, an amount of light beam directly reflected by a reflection/diffusion surface and emerging outside from the light emergent portion without total reflection is relatively large in all the light beam incident on the light guide member.
In particular, as in the conventional case, when the light-diffusing surface is a saw-toothed reflection surface and the saw-toothed projections are formed on the reflection surface at an equal pitch, part of the light beam directly emerging from the light emergent portion does not enter the pupil of the imaging lens, resulting in low illumination efficiency.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a light guide member wherein a light beam incident from a light incident surface, reflected by a saw-toothed reflection portion, and emerging from the light guide member can be focused at a predetermined focusing position to efficiently use the light beam, an illumination apparatus whose illumination efficiency is improved using the light guide member, and an image reading apparatus using the light guide member and illumination device.
A light guide member of the present invention is characterized by comprising a columnar light transmission member having an end face as a light incident surface, a light emergent surface on part of an outer surface of the columnar light transmission member, and a saw-toothed reflection portion on a surface opposing the light emergent surface,
wherein the saw-toothed reflection portion is made up of a plurality of reflection surfaces, and an angle of a reflection surface farther away from the light incident surface with respect to a longitudinal direction of the light guide member is larger than an angle of a reflection surface closer to the light incident surface with respect to the longitudinal direction.
A light guide member of the present invention is characterized by comprising a columnar light transmission member having an end face as a light incident surface, a light emergent surface on part of an outer surface of the columnar light transmission member, and a saw-toothed reflection portion on a surface opposing the light emergent surface,
wherein the saw-toothed reflection portion is made up of a plurality of reflection surfaces, each reflection surface is set to reflect the light beam from the light incident surface to a predetermined focusing position, and the following equation holds:
x
=(½)[{90°−tan
−1
(|
m|/D
)}−{tan
−1
(
H/|L|
)}]
for ±5° of a=90°−tan
−1
(
H/L
)−x
where
a: the tilt angle of the reflection surface with respect to the longitudinal direction of the light guide member
H: the distance between a light incident position of the light incident surface and the reflection surface in a section perpendicular to the longitudinal direction of the light guide member
L: the distance between the light incident surface of the light beam to be reflected and the reflection surface by which the light beam is reflected in the longitudinal direction of the light guide member
m: the distance between the focusing position and the reflection surface in the longitudinal direction of the light guide member
D: the distance between the focusing position and the reflection surface in a section perpendicular to the longitudinal direction of the light guide member.
A light guide member of the present invention is particularly characterized in that
the light guide member has a columnar shape,
the light incident surface is formed at each of two ends in the longitudinal direction,
the light incident surface is formed at one of two ends in the longitudinal direction, and an end reflection surface is formed on the other of the two ends,
the reflection surface has a reflectance of not less than 80%, or
the light emergent surface has a shape having a focusing function.
The light guide member of the present invention is particularly used in an illumination device for making a light beam from a light source incident on the light incident surface of the light guide member to illuminate an illumination target with the light beam emerging from the light emergent surface.
An illumination device using the light guide member of the present invention is characterized in that
the light source is an LED arranged at the light incident position of the light incident surface,
the light source is a monochromatic LED, or
the light source is made up of color LEDs.
The illumination device using the light guide member of the present invention is particularly used as illumination means for an image reading apparatus for making the light beam from an original illuminated with the illumination means incident on an imaging lens, guiding the light beam from the imaging lens onto a surface of a light-receiving element, forming an image of the original on the surface of the light-receiving element, and reading the image.
An imaging reading apparatus using the illumination device of the present invention is characterized in that
the imaging lens is located at the focusing position, or
a light beam transmitted through the original illuminated with the illumination device is incident on the imaging lens.
According to the light guide member having the above arrangement, the light beam incident on the light guide member is not totally reflected on the inner wall, but is directly reflected by the reflecting portion. The reflected light beam emerging outside the light guide member from the light emergent portion is efficiently focused at the predetermined focusing position. Therefore, the efficiency of the light beam focused by the lens located at the focusing position can be improved.
Since the light guide member has a columnar shape, the light beam from the light incident surface can be efficiently gu
Allen Stephone B.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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